Spatial control of vapor condensation using convection

ABSTRACT

Embodiments of the disclosed subject matter provide a device including a nozzle, a source of material to be deposited on a substrate in fluid communication with the nozzle, a delivery gas source in fluid communication with the source of material to be deposited with the nozzle, an exhaust channel disposed adjacent to the nozzle, and a confinement gas source in fluid communication with the nozzle and the exhaust channel, and disposed adjacent to the exhaust channel.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional PatentApplication Ser. No. 62/016,709, filed Jun. 25, 2014, the disclosure ofwhich is incorporated by reference in its entirety. This application isrelated to U.S. patent application Ser. No. 13/896,744, filed May 17,2013, the entire contents of which is incorporated herein by reference.

PARTIES TO A JOINT RESEARCH AGREEMENT

The claimed invention was made by, on behalf of, and/or in connectionwith one or more of the following parties to a joint universitycorporation research agreement: Regents of the University of Michigan,Princeton University, University of Southern California, and theUniversal Display Corporation. The agreement was in effect on and beforethe date the claimed invention was made, and the claimed invention wasmade as a result of activities undertaken within the scope of theagreement.

FIELD OF THE INVENTION

The present invention relates to organic light emitting devices (OLEDs)and, more specifically, to techniques for fabrication of such devicesusing convection of various gas flows. In particular, a gas curtainshaped by vacuum evacuation of a purge flow channel formed between a gasinjector assembly and a substrate. In some embodiments, this may be usedin combination with a nozzle adjacent to the vacuum evacuation channelto shape material flow. In other embodiments, the confinement gas doesnot need to be supplied through the nozzle, as the gas can come from theambient gas in a vacuum chamber (e.g., the vacuum evacuation channel).

BACKGROUND

Opto-electronic devices that make use of organic materials are becomingincreasingly desirable for a number of reasons. Many of the materialsused to make such devices are relatively inexpensive, so organicopto-electronic devices have the potential for cost advantages overinorganic devices. In addition, the inherent properties of organicmaterials, such as their flexibility, may make them well suited forparticular applications such as fabrication on a flexible substrate.Examples of organic opto-electronic devices include organic lightemitting devices (OLEDs), organic phototransistors, organic photovoltaiccells, and organic photodetectors. For OLEDs, the organic materials mayhave performance advantages over conventional materials. For example,the wavelength at which an organic emissive layer emits light maygenerally be readily tuned with appropriate dopants.

OLEDs make use of thin organic films that emit light when voltage isapplied across the device. OLEDs are becoming an increasinglyinteresting technology for use in applications such as flat paneldisplays, illumination, and backlighting. Several OLED materials andconfigurations are described in U.S. Pat. Nos. 5,844,363, 6,303,238, and5,707,745, which are incorporated herein by reference in their entirety.

One application for phosphorescent emissive molecules is a full colordisplay. Industry standards for such a display call for pixels adaptedto emit particular colors, referred to as “saturated” colors. Inparticular, these standards call for saturated red, green, and bluepixels. Color may be measured using CIE coordinates, which are wellknown to the art.

One example of a green emissive molecule is tris(2-phenylpyridine)iridium, denoted Ir(ppy)₃, which has the following structure:

In this, and later figures herein, we depict the dative bond fromnitrogen to metal (here, Ir) as a straight line.

As used herein, the term “organic” includes polymeric materials as wellas small molecule organic materials that may be used to fabricateorganic opto-electronic devices. “Small molecule” refers to any organicmaterial that is not a polymer, and “small molecules” may actually bequite large. Small molecules may include repeat units in somecircumstances. For example, using a long chain alkyl group as asubstituent does not remove a molecule from the “small molecule” class.Small molecules may also be incorporated into polymers, for example as apendent group on a polymer backbone or as a part of the backbone. Smallmolecules may also serve as the core moiety of a dendrimer, whichconsists of a series of chemical shells built on the core moiety. Thecore moiety of a dendrimer may be a fluorescent or phosphorescent smallmolecule emitter. A dendrimer may be a “small molecule,” and it isbelieved that all dendrimers currently used in the field of OLEDs aresmall molecules.

As used herein, “top” means furthest away from the substrate, while“bottom” means closest to the substrate. Where a first layer isdescribed as “disposed over” a second layer, the first layer is disposedfurther away from substrate. There may be other layers between the firstand second layer, unless it is specified that the first layer is “incontact with” the second layer. For example, a cathode may be describedas “disposed over” an anode, even though there are various organiclayers in between.

As used herein, “solution processable” means capable of being dissolved,dispersed, or transported in and/or deposited from a liquid medium,either in solution or suspension form.

A ligand may be referred to as “photoactive” when it is believed thatthe ligand directly contributes to the photoactive properties of anemissive material. A ligand may be referred to as “ancillary” when it isbelieved that the ligand does not contribute to the photoactiveproperties of an emissive material, although an ancillary ligand mayalter the properties of a photoactive ligand.

As used herein, and as would be generally understood by one skilled inthe art, a first “Highest Occupied Molecular Orbital” (HOMO) or “LowestUnoccupied Molecular Orbital” (LUMO) energy level is “greater than” or“higher than” a second HOMO or LUMO energy level if the first energylevel is closer to the vacuum energy level. Since ionization potentials(IP) are measured as a negative energy relative to a vacuum level, ahigher HOMO energy level corresponds to an IP having a smaller absolutevalue (an IP that is less negative). Similarly, a higher LUMO energylevel corresponds to an electron affinity (EA) having a smaller absolutevalue (an EA that is less negative). On a conventional energy leveldiagram, with the vacuum level at the top, the LUMO energy level of amaterial is higher than the HOMO energy level of the same material. A“higher” HOMO or LUMO energy level appears closer to the top of such adiagram than a “lower” HOMO or LUMO energy level.

As used herein, and as would be generally understood by one skilled inthe art, a first work function is “greater than” or “higher than” asecond work function if the first work function has a higher absolutevalue. Because work functions are generally measured as negative numbersrelative to vacuum level, this means that a “higher” work function ismore negative. On a conventional energy level diagram, with the vacuumlevel at the top, a “higher” work function is illustrated as furtheraway from the vacuum level in the downward direction. Thus, thedefinitions of HOMO and LUMO energy levels follow a different conventionthan work functions.

More details on OLEDs, and the definitions described above, can be foundin U.S. Pat. No. 7,279,704, which is incorporated herein by reference inits entirety.

SUMMARY OF THE INVENTION

An embodiment of the disclosed subject matter provides a deviceincluding a nozzle, a source of material to be deposited on a substratein fluid communication with the nozzle, a delivery gas source in fluidcommunication with the source of material to be deposited with thenozzle, an exhaust channel disposed adjacent to the nozzle, and aconfinement gas source in fluid communication with the nozzle and theexhaust channel, and disposed adjacent to the exhaust channel.

Another embodiment of the disclosed subject matter provides a methodincluding ejecting a delivery gas and a material to be deposited on asubstrate from a nozzle, providing a confinement gas having a flowdirection opposing a flow direction of the delivery gas ejected from thenozzle, and providing a vacuum source adjacent to a delivery gasaperture of the nozzle.

Another embodiment of the disclosed subject matter provides a nozzleassembly including a plurality of nozzles, with each nozzle comprisingat least three separate types of flow channels which include a deliverychannel to provide a delivery gas including an organic material, exhaustchannels arranged adjacent to the delivery channel to evacuate gas froman area disposed between the nozzle assembly and a substrate, andconfinement gas channels arranged adjacent to the exhaust channels tosupply a confinement gas flow.

Another embodiment of the disclosed subject matter includes providing amethod including forming a nozzle assembly having a plurality ofnozzles, with each nozzle comprising at least three separate types offlow channels, including forming a first channel to provide a deliverygas including an organic material, forming a plurality of secondchannels arranged adjacent to the first channel to evacuate gas from anarea disposed between the nozzle assembly and a substrate, and forming aplurality of confinement gas channels arranged adjacent to the pluralityof second channels to supply a confinement gas flow.

Another embodiment of the disclosed subject matter provides a depositionsystem including a nozzle assembly having a plurality of nozzles, witheach nozzle comprising at least three separate types of flow channelswhich include a first channel to provide a delivery gas including anorganic material, a plurality of second channels arranged adjacent tothe first channel to evacuate gas from an area disposed between thenozzle assembly and a substrate, and a pair of confinement gas channelsarranged adjacent to the plurality of second channels to supply aconfinement gas flow.

Another embodiment of the disclosed subject matter provides a displayfabricated using a nozzle assembly to deposit organic materials, thenozzle assembly having a plurality of nozzles, with each nozzlecomprising a plurality of separate types of flow channels which includea first channel to provide a delivery gas including an organic material,a plurality of second channels arranged adjacent to the first channel toevacuate gas from an area disposed between the nozzle assembly and asubstrate, and a plurality of confinement gas channels arranged adjacentto the plurality of second channels to supply a confinement gas flow.

According to another embodiment, a first device comprising a firstorganic light emitting device is also provided. The first organic lightemitting device can include an anode, a cathode, and an organic layer,disposed between the anode and the cathode. The organic layer can beformed by a device including a nozzle, a source of material to bedeposited on a substrate in fluid communication with the nozzle, adelivery gas source in fluid communication with the source of materialto be deposited with the nozzle, an exhaust channel disposed adjacent tothe nozzle, and a confinement gas source in fluid communication with thenozzle and the exhaust channel, and disposed adjacent to the exhaustchannel. The first device can be a consumer product, an organiclight-emitting device, and/or a lighting panel.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an organic light emitting device.

FIG. 2 shows an inverted organic light emitting device that does nothave a separate electron transport layer.

FIG. 3 shows a schematic representation of overspray in a conventionalOVJP or similar system.

FIG. 4 shows a cross sectional diagram of a deposition structureaccording to an embodiment of the disclosed subject matter.

FIG. 5 shows example streamlines of delivery gas flow according to anembodiment of the disclosed subject matter.

FIG. 6 shows a plot of organic vapor concentration in a flow fieldaccording to an embodiment of the disclosed subject matter.

FIG. 7A shows the thickness of thin film lines as a function of in-planedistance from the nozzle centerline according to conventional oversprayreduction technology for depositing materials with non-unity stickingcoefficient.

FIG. 7B shows the thickness of thin film lines as a function of in-planedistance from the nozzle centerline according to an embodiment of thedisclosed subject matter.

FIG. 8 shows a conventional organic vapor jet printing (OVJP) system.

FIG. 9 shows a cross-sectional thickness profile from a conventionalOVJP system.

FIG. 10A shows stream lines emanating from four nozzles of aconventional linear array.

FIG. 10B shows a resulting deposition profile from the emanated streamlines of FIG. 10A of the conventional linear array.

FIG. 11 shows an OVJP nozzle array according to an embodiment of thedisclosed subject matter.

FIG. 12 shows stream lines of confinement gas flows entering from theirrespective sources, intersecting a region between a print head and anozzle assembly, and exiting through an exhaust channel according to anembodiment of the disclosed subject matter.

FIG. 13 shows a bifurcated delivery channel according to an embodimentof the disclosed subject matter.

FIG. 14A shows an aperture configuration of a three element nozzleassembly according to an embodiment of the disclosed subject matter.

FIG. 14B shows a cross section view of flow channels on the nozzleassembly of FIG. 14A according to an embodiment of the disclosed subjectmatter.

FIG. 14C shows a balanced flow from the nozzle assembly according to anembodiment of the disclosed subject matter.

FIG. 14D shows a modeled thickness distribution of a three elementnozzle array of four nozzles according to an embodiment of the disclosedsubject matter.

FIG. 15 shows a two dimensional array with deposition apertures alignedso that a deposition from the apertures in successive rows adds to thedeposition from the first row according to an embodiment of thedisclosed subject matter.

FIG. 16 shows a two dimensional array with both aligned and staggereddeposition nozzles according to an embodiment of the disclosed subjectmatter.

FIG. 17 shows a nozzle assembly that includes confinement distributionchannels according to an embodiment of the disclosed subject matter.

FIG. 18 shows spatially resolved flux of organic material from a nozzleassembly onto a substrate predicted by a computational fluid dynamicsmodel according to an embodiment of the invention.

FIG. 19 shows a scanning electron micrograph of the interior channels ofa nozzle assembly etched from a silicon (Si) wafer according to anembodiment of the disclosed subject matter.

FIG. 20A shows a micrograph of the substrate-facing edge of a Si dieaccording to an embodiment of the disclosed subject matter, includingthe nozzle, exhaust apertures, and other features.

FIG. 20B shows a schematic illustration of an OLED structure fabricatedaccording to an embodiment of the invention.

FIG. 21A shows an example of a line of electroluminescent materialprinted by a technique according to an embodiment of the disclosedsubject matter.

FIG. 21B shows an example of a line of electroluminescent materialprinted by a conventional technique used previous to the invention.

DETAILED DESCRIPTION

Generally, an OLED comprises at least one organic layer disposed betweenand electrically connected to an anode and a cathode. When a current isapplied, the anode injects holes and the cathode injects electrons intothe organic layer(s). The injected holes and electrons each migratetoward the oppositely charged electrode. When an electron and holelocalize on the same molecule, an “exciton,” which is a localizedelectron-hole pair having an excited energy state, is formed. Light isemitted when the exciton relaxes via a photoemissive mechanism. In somecases, the exciton may be localized on an excimer or an exciplex.Non-radiative mechanisms, such as thermal relaxation, may also occur,but are generally considered undesirable.

The initial OLEDs used emissive molecules that emitted light from theirsinglet states (“fluorescence”) as disclosed, for example, in U.S. Pat.No. 4,769,292, which is incorporated by reference in its entirety.Fluorescent emission generally occurs in a time frame of less than 10nanoseconds.

More recently, OLEDs having emissive materials that emit light fromtriplet states (“phosphorescence”) have been demonstrated. Baldo et al.,“Highly Efficient Phosphorescent Emission from OrganicElectroluminescent Devices,” Nature, vol. 395, 151-154, 1998;(“Baldo-I”) and Baldo et al., “Very high-efficiency green organiclight-emitting devices based on electrophosphorescence,” Appl. Phys.Lett., vol. 75, No. 3, 4-6 (1999) (“Baldo-II”), which are incorporatedby reference in their entireties. Phosphorescence is described in moredetail in U.S. Pat. No. 7,279,704 at cols. 5-6, which are incorporatedby reference.

FIG. 1 shows an organic light emitting device 100. The figures are notnecessarily drawn to scale. Device 100 may include a substrate 110, ananode 115, a hole injection layer 120, a hole transport layer 125, anelectron blocking layer 130, an emissive layer 135, a hole blockinglayer 140, an electron transport layer 145, an electron injection layer150, a protective layer 155, a cathode 160, and a barrier layer 170.Cathode 160 is a compound cathode having a first conductive layer 162and a second conductive layer 164. Device 100 may be fabricated bydepositing the layers described, in order. The properties and functionsof these various layers, as well as example materials, are described inmore detail in U.S. Pat. No. 7,279,704 at cols. 6-10, which areincorporated by reference.

More examples for each of these layers are available. For example, aflexible and transparent substrate-anode combination is disclosed inU.S. Pat. No. 5,844,363, which is incorporated by reference in itsentirety. An example of a p-doped hole transport layer is m-MTDATA dopedwith F₄-TCNQ at a molar ratio of 50:1, as disclosed in U.S. PatentApplication Publication No. 2003/0230980, which is incorporated byreference in its entirety. Examples of emissive and host materials aredisclosed in U.S. Pat. No. 6,303,238 to Thompson et al., which isincorporated by reference in its entirety. An example of an n-dopedelectron transport layer is BPhen doped with Li at a molar ratio of 1:1,as disclosed in U.S. Patent Application Publication No. 2003/0230980,which is incorporated by reference in its entirety. U.S. Pat. Nos.5,703,436 and 5,707,745, which are incorporated by reference in theirentireties, disclose examples of cathodes including compound cathodeshaving a thin layer of metal such as Mg:Ag with an overlyingtransparent, electrically-conductive, sputter-deposited ITO layer. Thetheory and use of blocking layers is described in more detail in U.S.Pat. No. 6,097,147 and U.S. Patent Application Publication No.2003/0230980, which are incorporated by reference in their entireties.Examples of injection layers are provided in U.S. Patent ApplicationPublication No. 2004/0174116, which is incorporated by reference in itsentirety. A description of protective layers may be found in U.S. PatentApplication Publication No. 2004/0174116, which is incorporated byreference in its entirety.

FIG. 2 shows an inverted OLED 200. The device includes a substrate 210,a cathode 215, an emissive layer 220, a hole transport layer 225, and ananode 230. Device 200 may be fabricated by depositing the layersdescribed, in order. Because the most common OLED configuration has acathode disposed over the anode, and device 200 has cathode 215 disposedunder anode 230, device 200 may be referred to as an “inverted” OLED.Materials similar to those described with respect to device 100 may beused in the corresponding layers of device 200. FIG. 2 provides oneexample of how some layers may be omitted from the structure of device100.

The simple layered structure illustrated in FIGS. 1 and 2 is provided byway of non-limiting example, and it is understood that embodiments ofthe invention may be used in connection with a wide variety of otherstructures. The specific materials and structures described areexemplary in nature, and other materials and structures may be used.Functional OLEDs may be achieved by combining the various layersdescribed in different ways, or layers may be omitted entirely, based ondesign, performance, and cost factors. Other layers not specificallydescribed may also be included. Materials other than those specificallydescribed may be used. Although many of the examples provided hereindescribe various layers as comprising a single material, it isunderstood that combinations of materials, such as a mixture of host anddopant, or more generally a mixture, may be used. Also, the layers mayhave various sublayers. The names given to the various layers herein arenot intended to be strictly limiting. For example, in device 200, holetransport layer 225 transports holes and injects holes into emissivelayer 220, and may be described as a hole transport layer or a holeinjection layer. In one embodiment, an OLED may be described as havingan “organic layer” disposed between a cathode and an anode. This organiclayer may comprise a single layer, or may further comprise multiplelayers of different organic materials as described, for example, withrespect to FIGS. 1 and 2.

Structures and materials not specifically described may also be used,such as OLEDs comprised of polymeric materials (PLEDs) such as disclosedin U.S. Pat. No. 5,247,190 to Friend et al., which is incorporated byreference in its entirety. By way of further example, OLEDs having asingle organic layer may be used. OLEDs may be stacked, for example asdescribed in U.S. Pat. No. 5,707,745 to Forrest et al, which isincorporated by reference in its entirety. The OLED structure maydeviate from the simple layered structure illustrated in FIGS. 1 and 2.For example, the substrate may include an angled reflective surface toimprove out-coupling, such as a mesa structure as described in U.S. Pat.No. 6,091,195 to Forrest et al., and/or a pit structure as described inU.S. Pat. No. 5,834,893 to Bulovic et al., which are incorporated byreference in their entireties.

Unless otherwise specified, any of the layers of the various embodimentsmay be deposited by any suitable method. For the organic layers,preferred methods include thermal evaporation, ink-jet, such asdescribed in U.S. Pat. Nos. 6,013,982 and 6,087,196, which areincorporated by reference in their entireties, organic vapor phasedeposition (OVPD), such as described in U.S. Pat. No. 6,337,102 toForrest et al., which is incorporated by reference in its entirety, anddeposition by organic vapor jet printing (OVJP), such as described inU.S. Pat. No. 7,431,968, which is incorporated by reference in itsentirety. Other suitable deposition methods include spin coating andother solution based processes. Solution based processes are preferablycarried out in nitrogen or an inert atmosphere. For the other layers,preferred methods include thermal evaporation. Preferred patterningmethods include deposition through a mask, cold welding such asdescribed in U.S. Pat. Nos. 6,294,398 and 6,468,819, which areincorporated by reference in their entireties, and patterning associatedwith some of the deposition methods such as ink-jet and OVJD. Othermethods may also be used. The materials to be deposited may be modifiedto make them compatible with a particular deposition method. Forexample, substituents such as alkyl and aryl groups, branched orunbranched, and preferably containing at least 3 carbons, may be used insmall molecules to enhance their ability to undergo solution processing.Substituents having 20 carbons or more may be used, and 3-20 carbons isa preferred range. Materials with asymmetric structures may have bettersolution processability than those having symmetric structures, becauseasymmetric materials may have a lower tendency to recrystallize.Dendrimer substituents may be used to enhance the ability of smallmolecules to undergo solution processing.

Devices fabricated in accordance with embodiments of the presentinvention may further optionally comprise a barrier layer. One purposeof the barrier layer is to protect the electrodes and organic layersfrom damaging exposure to harmful species in the environment includingmoisture, vapor and/or gases, etc. The barrier layer may be depositedover, under or next to a substrate, an electrode, or over any otherparts of a device including an edge. The barrier layer may comprise asingle layer, or multiple layers. The barrier layer may be formed byvarious known chemical vapor deposition techniques and may includecompositions having a single phase as well as compositions havingmultiple phases. Any suitable material or combination of materials maybe used for the barrier layer. The barrier layer may incorporate aninorganic or an organic compound or both. The preferred barrier layercomprises a mixture of a polymeric material and a non-polymeric materialas described in U.S. Pat. No. 7,968,146, PCT Pat. Application Nos.PCT/US2007/023098 and PCT/US2009/042829, which are herein incorporatedby reference in their entireties. To be considered a “mixture”, theaforesaid polymeric and non-polymeric materials comprising the barrierlayer should be deposited under the same reaction conditions and/or atthe same time. The weight ratio of polymeric to non-polymeric materialmay be in the range of 95:5 to 5:95. The polymeric material and thenon-polymeric material may be created from the same precursor material.In one example, the mixture of a polymeric material and a non-polymericmaterial consists essentially of polymeric silicon and inorganicsilicon.

Devices fabricated in accordance with embodiments of the invention canbe incorporated into a wide variety of electronic component modules (orunits) that can be incorporated into a variety of electronic products orintermediate components. Examples of such electronic products orintermediate components include display screens, lighting devices suchas discrete light source devices or lighting panels, etc. that can beutilized by the end-user product manufacturers. Such electroniccomponent modules can optionally include the driving electronics and/orpower source(s). Devices fabricated in accordance with embodiments ofthe invention can be incorporated into a wide variety of consumerproducts that have one or more of the electronic component modules (orunits) incorporated therein. Such consumer products would include anykind of products that include one or more light source(s) and/or one ormore of some type of visual displays. Some examples of such consumerproducts include flat panel displays, computer monitors, medicalmonitors, televisions, billboards, lights for interior or exteriorillumination and/or signaling, heads-up displays, fully or partiallytransparent displays, flexible displays, laser printers, telephones,cell phones, tablets, phablets, personal digital assistants (PDAs),laptop computers, digital cameras, camcorders, viewfinders,micro-displays, 3-D displays, vehicles, a large area wall, theater orstadium screen, or a sign. Various control mechanisms may be used tocontrol devices fabricated in accordance with the present invention,including passive matrix and active matrix. Many of the devices areintended for use in a temperature range comfortable to humans, such as18° C. to 30° C., and more preferably at room temperature (20°-25° C.),but could be used outside this temperature range, for example, from −40°C. to +80° C.

The materials and structures described herein may have applications indevices other than OLEDs. For example, other optoelectronic devices suchas organic solar cells and organic photodetectors may employ thematerials and structures. More generally, organic devices, such asorganic transistors, may employ the materials and structures.

Although U.S. Provisional Patent Application Ser. No. 62/016,709, fromwhich this application claims priority and is incorporated by referenceherein, may utilize different terms than the present application, thereis no difference in the meaning of the terms. For example, purge gas maybe referred as confinement gas in the present application, carrier gasmay be referred to as delivery gas, evacuation channels may be referredto as exhaust channels, a carrier gas nozzle may be referred to as adelivery aperture, a sweep gas may be referred to as a confinement gas,a nozzle orifice may be referred to as a nozzle aperture or deliverychannel, and a vacuum vent may be referred to as an exhaust channel, andthe like.

As utilized herein, the terms confinement flow and/or confinement gasrefer to gases and gas flows that may come in from outside of adeposition zone and may reduce the spread of organic vapor by opposingan in-substrate plane motion of a delivery gas flow. Confinement flowand/or confinement gas may drive surplus organic material into exhaustapertures that are coupled to exhaust channels. That is, a confinementflow may include a confinement gas, which generally has a highermolecular weight than a delivery gas.

A confinement gas may be drawn from a chamber ambient or introducedthrough specialized nozzles (e.g., confinement apertures that arecoupled to confinement channels). When the confinement gas comes fromthe chamber, the confinement channel may be the gap underneath a nozzlearray at fly height, which may be the gap between the nozzle andsubstrate.

A delivery aperture may be the intersection of the delivery channel andthe edge of the print head proximal to the substrate. It may besubdivided to smaller apertures.

A delivery flow and/or delivery gas may entrain organic vapor fromsource ovens and carry it through a delivery channel to a depositionzone on a substrate proximal to a print head tip. The delivery flow canbe a mixture of flows from multiple source ovens. The delivery gas maybe helium and/or any other suitable gas.

A delivery channel may lead organic vapor from one or more sourcestowards the substrate. The delivery channel may be generally orientedalong the substrate normal, but it can also be angled. The deliverychannel intersection with the print head edge may define the deliveryaperture.

An exhaust aperture and/or exhaust channel may surround the deliverychannel. It can be oriented in parallel with the delivery channel orangled relative to it. Typically the exhaust is configured to removedelivery gas from a deposition zone. When a confinement gas is present,the confinement flow established between the confinement flow source andthe exhaust channel removes surplus organic vapor from the depositionzone. The exhaust channel intersection with the print head edge definesthe exhaust aperture.

A nozzle may be a single, microfabricated unit of a nozzle assemblyincluding the delivery and exhaust apertures, as well as the confinementapertures when present.

A nozzle block may be one-piece microfabricated assembly having one ormore nozzles. The nozzle block may be held over the substrate by aheated clamp.

A print head may include the nozzle block and the heated holdercontaining the fluid connections necessary to interface the nozzle blockwith one or more sources such as source ovens, an exhaust line to theoutside of the chamber, and a confinement gas source.

As previously described, various techniques may be used to fabricateOLEDs and other similar devices, including organic vapor jet printing(OVJP). In OVJP, patterned arrays of organic thin film features may bedeposited without the use of liquid solvents or shadow masks. An inertdelivery gas transports organic vapor from evaporation sources to anozzle array. The nozzle array generates a jet of gas-vapor mixture thatimpinges on a substrate. The organic vapor condenses on the substrate ina well-defined spot. Features can be drawn by moving the substraterelative to the print head. Co-deposition of host and dopant, as may bedesirable for phosphorescent OLEDs, can be achieved by mixing vaporsfrom different sources upstream of the nozzle. Microfabricated nozzlearrays have been demonstrated to achieve printing resolution comparableto that required for display applications.

Deposition of organic material beyond the intended boundaries of aprinted feature, or overspray, is a frequent problem of OVJP. A moleculeof organic vapor that comes into contact with the substrate can eitherirreversibly adsorb to it or reflect away from it. Adsorbed materialcondenses to become part of a printed feature. Material that does notcondense is scattered back into the surrounding gas ambient. Thesticking coefficient α is defined as the probability that a molecule oforganic vapor condenses per encounter with the substrate. Stickingcoefficients of 0.8 to 0.9 are typical of OLED materials.

Molecules of organic vapor may reflect away from the substrate ratherthan adsorbing to it. This may cause deposition beyond intendedboundaries, since the vapor has the potential to contaminate neighboringfeatures. A variety of transport mechanisms may carry dilute organicvapor away from the nozzle. When the gas flow is dominated byintermolecular interactions, i.e. for Knudsen numbers Kn less than 1(Kn=λ/l, where λ is the mean free path in the delivery gas field and lis the characteristic length of the nozzle assembly), the organic vaporplume emanating from the nozzle is broadened by both convection anddiffusion. When Kn is greater than 1, printed features are broadened byballistic motion of vapor molecules transverse to the substrate normal.In either case, feature broadening may be exacerbated if organicmolecules do not adsorb upon contact with the substrate.

Convective and diffusive broadening may be minimized by operating anOVJP process at a very low background pressure, for example, less than10-4 Torr. However, overspray may persist due to non-unity α as shown inFIG. 3. Fine features may be printed with OVJP, for example, by placinga heated nozzle array 301 close to the substrate 302. Organic moleculesthat fail to adsorb on the substrate 302 may reflect back onto theunderside of the nozzle array 301 and become scattered beyond thedesired printing area 303. Organic molecules that may initially adsorb(e.g., molecules 304) to the substrate 302 stay within the desiredprinting area 303, while molecules that do not adsorb (e.g., molecules305) may be scattered further afield. The nozzle of the nozzle array 301may be heated so that organic molecules (e.g., molecules 305) do notstick to its underside, and instead may be redirected onto the substrate302 where they may land outside of the desired deposition area (e.g.,desired printing area 303). Thus, it is desirable for material that doesnot adsorb to the substrate to be rapidly removed to minimize and/orprevent feature broadening, as described in further detail herein.

FIG. 4 shows a cross sectional diagram of a deposition structure (e.g.,a nozzle assembly 400) according to an embodiment of the disclosedsubject matter. A delivery channel 401 may be adjacent to, or surroundedby one or more exhaust channels 402. A delivery gas transporting amaterial to be deposited on a substrate 302 may be ejected from anaperture of the delivery channel 401 toward the substrate 302. Organicmolecules that do not adsorb to the substrate (e.g., molecules 305) maybe removed through the exhaust channel 402. A confinement gas 403 may beprovided in a direction opposing the flow of material ejected from theaperture of the delivery channel of the nozzle. The confinement gas 403may be provided from a source, such as a nozzle, an ambient source, orthe like, from a location below the nozzle (i.e., between an aperture ofthe nozzle and the substrate 302) and adjacent to the nozzle and/or theexhaust channel 402. In some configurations, the confinement gas may beprovided via a nozzle that is integrated with or integrally part of thenozzle block. Such a nozzle may be used even where the confinement gasflow is provided from the ambient environment. For example, a nozzleblock may include one or more channels etched into the bottom of thenozzle block, through which the confinement gas 403 may be directed. Oneor more external nozzles (i.e., that are not integral with the nozzleblock) may be used to direct the confinement gas into the depositionregion. The confinement gas provided to the region between the nozzleassembly 400 and the substrate 302 may be chilled, such that it has anaverage temperature lower than the ambient temperature of a chamber inwhich the deposition is performed. It also may be provided at ambienttemperature, or at a temperature higher than ambient.

The confinement gas may flow inward from the outside of the depositionzone and guide surplus material into the exhaust channels 402. Theconfinement gas flow may oppose the flow of material ejected from thenozzle if the majority of the confinement gas flow is primarily in adirection anti-parallel to a direction in which the majority of thematerial ejected from the nozzle flows. Flow out of the nozzle (e.g.,the delivery channel 401) in the deposition zone may be primarilydefined by the gap between the nozzle block and substrate 301, ratherthan by the geometry of the nozzle itself. A confinement gas flow in theplane of the substrate 302 can therefore be considered to oppose anozzle flow (e.g., a flow from an aperture of the delivery channel 401),regardless of the orientation of the nozzle. For example, if the nozzle(e.g., an aperture of the delivery channel 401) is oriented to ejectmaterial in a direction perpendicular to the plane of the substrate 302,material ejected from the nozzle is redirected by the substrate 302 sothat it travels in the plane of the substrate 302. Ejected material isthen redirected out of the plane of the substrate 302 further downstreamfrom the nozzle (e.g., the aperture of the delivery channel 401) whereit intersects a confinement gas flow moving in the opposite direction.The stream of confinement gas can originate either from the chamberambient or from dedicated nozzles connected to an external gas source.

The exhaust channel 402 may be connected to a vacuum source, i.e., asource of pressure lower than that of the region between the nozzle(e.g., an aperture of the delivery channel 401) and the substrate 302.The vacuum source may be external to the deposition structure (e.g., thenozzle assembly 400). For example, the nozzle block or other depositionmechanism may include a connector configured to connect the exhaustchannel 402 to an external vacuum source. The exhaust channel 402 may beangled, relative to the delivery channel 401, to allow sufficientmaterial between the exhaust channel 402 and the delivery channel 401within the nozzle block. This configuration may provide sufficientmaterial in the nozzle block between the channels (e.g., the deliverychannel 401 and the exhaust channel 402) for the nozzle block to bestructurally sound. The exhaust channel 402 within the nozzle block maybe angled relative to the delivery channel 401. Such a configuration mayimprove the uniformity of the deposited material on the substrate.Compared to a “straight” exhaust channel passage with an axis of flownormal to the substrate, an angled passage may minimize and/or preventformation of sharp angle through which the confinement gas, deliverygas, and/or undeposited material would have to flow, as shown in furtherdetail in the examples and simulations disclosed herein.

The exhaust channel 402 may surround the nozzle passage (e.g., thedelivery channel 401) within the nozzle block (e.g., the nozzle assembly400). For example, the exhaust channel 402 may be of sufficient widthwithin the nozzle block (e.g., the nozzle assembly 400) such that thesmallest distance between the delivery channel 401 and the exhaustchannel 402 is the same in at least two directions relative to thenozzle. In some configurations, the nozzle aperture may be defined bythe planar edge of the nozzle block and a channel within the nozzleblock. That is, a nozzle as disclosed herein may not require anadditional tapered and/or other extended physical portion that extendsbeyond a lower surface of the nozzle block.

The nozzle aperture (e.g., delivery channel 401) can be bifurcated orotherwise divided by delivery channel separator 404 to include multipleapertures (e.g., multiple delivery channels 401, as shown in FIG. 4).The delivery channel 401 that is divided by the delivery channelseparator 404 may improve the uniformity of organic material flux ontothe substrate 302 within the deposition zone. For example, withoutbifurcation (e.g., without the presence of the delivery channelseparator 404), a raised or rounded deposition profile may result. Incontrast, when the nozzle is bifurcated (e.g., the delivery channel 401is divided by the delivery channel separator 404), the blocking materialin the center of the nozzle may prevent material from depositing in themiddle of the deposition area, leading to a flatter, “plateau” typedeposition profile. More generally, a nozzle as disclosed herein mayinclude multiple apertures.

Nozzles as disclosed herein may be oriented vertically, i.e., positionedsuch that the axis of the delivery channel is perpendicular to asubstrate on which material ejected by the nozzle is to be deposited.Alternatively or in addition, one or more nozzles may be positioned atan angle relative to the substrate, such as an angle between 0° and 90°.

A nozzle block as disclosed herein may include multiple deliveryapertures and/or multiple exhaust channels, which may be disposed in anysuitable arrangement within the nozzle block. For example, multipledelivery apertures may be disposed within a nozzle block, with exhaustchannels disposed between adjacent nozzles. When multiple nozzles areused within a single nozzle block, they may be disposed in any suitablearrangement, such as a linear, staggered, or layered arrangement. Eacharrangement of nozzles may be used to perform different ordered orsimultaneous deposition. For example, in a linear arrangement, eachnozzle may deposit a different layer over a single substrate that ismoved past each nozzle in the linear arrangement in turn.

In some embodiments of the disclosed subject matter, the nozzle block,or a portion of the nozzle block, may be heated to a temperature higherthan the evaporation point of the least volatile organic material in thedelivery gas ejected by the nozzles. This may further minimize and/orprevent the material from condensing on various parts of the depositionapparatus.

Deposition systems as disclosed herein also may include a substrateholder or other arrangement configured to position the substrate 302below the nozzle (e.g., the delivery channel 401). In someconfigurations, the substrate holder may be positioned relative to thenozzle such that a substrate 302 placed on the substrate holder ispositioned about 10-1000 μm below the nozzle aperture.

In some embodiments of the disclosed subject matter, a chiller plate(e.g., a thermoelectric cooler) or other lower-temperature device orregion may be disposed adjacent to the nozzle surface (e.g., the surfacehaving an aperture of the delivery channel 401) of the nozzle block(e.g., the nozzle assembly 400). For example, a chiller plate may bedisposed adjacent to the lower surface of a nozzle block facing thesubstrate 302, adjacent to one or more nozzles. A chiller plate also maybe disposed adjacent to the nozzle block, but may not be in physicalcontact with the nozzle block.

In some embodiments of the disclosed subject matter, the depositionsystems and techniques disclosed herein may be performed within adeposition chamber. The chamber may be filled with one or more gases,which may be used to provide the confinement gas flow as previouslydisclosed. In some embodiments, the deposition chamber may be filledwith one or more gases, such that the ambient environment in the chamberhas a composition different from that of the confinement gas and/or thedelivery gas or gases used as disclosed herein. The deposition chambermay be maintained at any suitable pressure, including 10 Torr, 100 Torr,760 Torr, or the like.

Deposition systems as disclosed herein may be used to deposit variouscomponents of OLED or similar devices as previously disclosed.Alternatively, or in addition, they may be rastered across a substrateso as to deposit a uniform film of material on the substrate. Forexample, the deposition system may include an alignment system thatrasters one or more nozzles based upon the existence and position offiducial marks on the substrate.

FIG. 5 shows example streamlines of delivery gas flow according to anembodiment of the disclosed subject matter. The delivery flow 501follows streamlines connecting the aperture of the delivery channel 401with the exhaust channel 402. The confinement gas flow 502 followsstreamlines connecting gas inlet 403 to the exhaust channel 402.

The confinement gas flow 502 generally opposes the delivery flow 501.The flows intersect 503 and turn toward the exhaust channel 402. This inturn forms a barrier, which may be referred to as a “gas curtain”, tothe spread of organic material along the plane of the substrate (e.g.,substrate 302 of FIG. 4). Organic vapor that does not condense on thesubstrate under the nozzle in region 504 may remain entrained within thedelivery gas flow 505 entering the exhaust (e.g., exhaust channel 402 ofFIG. 4). The material is then removed from the deposition area as thisflow passes through the exhaust (e.g., the exhaust channel 402 shown inFIG. 4).

FIG. 6 shows a plot of the concentration of organic vapor in the flowfield. As shown, a plume containing a high concentration of organicvapor 601 may emanate from the delivery aperture. The material in thisplume diffusively transports across a concentration gradient 602 towardsthe substrate. The remainder of the vapor is transported from thesubstrate with portion of the plume exiting the exhaust via 603. Organicvapor that does diffuse across streamlines into the confinement gas flowmay be removed through the exhaust channel as the confinement gas exits.Convection from the confinement gas flow drives organic vapor upward andaway from the substrate. Transport of organic vapor onto regions ofsubstrate covered by the confinement gas flow, therefore, may benegligible.

The Peclet number Pe may be used to describe the ratio of convective anddiffusive transport in such a flow:

Pe=lu/D,

where l is the characteristic length, u is the characteristic velocity,and D is the diffusivity of organic vapor in the gas ambient. In anarrangement as described with respect to FIGS. 3-6, Pe is on the orderof 1-10 underneath the nozzle, and 10-100 in the confinement gas flow.Convective transport therefore dominates in the confinement gas stream,permitting effective removal of organic vapor through the exhaustchannel.

The effectiveness of this convective transport technique, particularlywhen depositing organic components with sticking coefficients less than1, is shown in FIGS. 7A and 7B. As shown in FIG. 7A, very sharplydefined features 701 can be achieved when α=1. There is significantbroadening and the intended features are surrounded by broad overspraytails for the cases of α=0.5 (702) and α=0.1 (703), as shown in FIG. 7A.As shown in FIG. 7B, a gas curtain technique as disclosed herein mayresult in a wider feature profile for the case of α=1 (704) than for aplain nozzle, but that deposition profile may remain nearly unchangedfor α=0.5 (705) and α=0.1 (706). That is, the overspray mitigationcapability of the gas curtain may be nearly independent of stickingcoefficient, making it suitable for depositing a wider range of OLEDmaterials.

Deposition systems of the embodiments of the disclosed subject mattermay be fabricated using any suitable technique. For example, thefeatures of the nozzle block may be etched into a silicon wafer usingphotolithography, reactive ion etching, or the like. The structure alsomay be fabricated by etching channels into multiple wafers that are thenbonded together to form the desired three-dimensional structures, forexample, using wafer bonding and/or optical alignment techniques.Suitable wafer bonding techniques may include, for example, anodic, goldeutectic, solder, Si fusion, and the like. As another example,individual dies may be singulated, such as by stealth dicing, to from awafer structure, allowing for the nozzle tips, exhaust channels, andother ports on a nozzle block to be defined by the die edges.

Organic materials used to manufacture OLED displays are typicallydeposited by vacuum thermal evaporation (VTE) through shadow masks.Shadow masks may be fabricated from thin metal sheets which arestretched on frames and subsequently aligned to patterns on thesubstrate. Perforations in the shadow mask may define the area of thesubstrate that will be covered by deposition. For large area displays,shadow masks are typically difficult to use due to mask heating andsagging, which may adversely affect yield.

Organic Vapor Jet Printing (OVJP) is a vapor deposition technology thatis capable of printing narrow, pixel width lines over large areaswithout the use of shadow masks. Organic vapors entrained in an inertdelivery gas may be ejected from a nozzle and impinge on a substratewhere the vapors condense, resulting in a deposited film. The design ofthe nozzle may determine the size and shape of the deposit.

FIG. 8 shows a first generation OVJP system that uses a round nozzleformed in metal or glass with a size limited to about 0.3 mm indiameter, which is capable of depositing lines of several mm in width.The cross sectional thickness profile related to such a nozzle is shownin FIG. 9. To deposit lines using a single OVJP nozzle, such as tomanufacture a large area display, or form two-dimensional patterns, thenozzle is typically rastered over the substrate, or the substrate israstered under a stationary nozzle. As a specific example, highdefinition 4K HD displays typically have 3840 rows of vertical pixels.Printing such a display, one row at a time with a single nozzle, may bevery time consuming. The desired time to complete each display step(TAKT time) may be on the order of 2-5 minutes. To meet the TAKT timerequirement, an array of nozzles would be required.

Depositions using individual or isolated OVJP nozzles have beenanalyzed, but such analysis typically ignores the effects of gas flowand deposition patterns caused by neighboring nozzles. The depositionpatterns from isolated nozzles may exhibit a Gaussian thickness profileas shown in FIG. 9. The width of the pattern may be a function of thenozzle diameter, the distance between the nozzle and substrate, thedeposition chamber pressure, and the flow of delivery gas and organicvapor. For this type of simple nozzle, the deposition profile width istypically much wider than the nozzle diameter. Experimental results havebeen obtained from single nozzles, or from arrays of nozzles, withnozzles separated by 2 mm or more to eliminate neighbor effects. Whennozzles are placed in close proximity (e.g., with a range of severalhundred microns), gas flowing from one nozzle can alter the depositionpattern of neighboring nozzles. To achieve the desired TAKT time toproduce a large area display, many nozzles must be used. To achieve thedesired pixel dimensions, the nozzles must be placed close together,where neighbor effects will dominate the deposition profiles.

Organic material may be carried from the sublimation source to thenozzle in a delivery gas, which does not condense on the substratesurface. In a two-dimensional array of nozzles in a vacuum chamber, thenozzles in the center of the array may experience a higher backgroundpressure than nozzles at the periphery due to conductance limitations ofthe small gap between the substrate and nozzle array. For large arrays(e.g., arrays having about five or more nozzles), and substrate tonozzle array gaps that are much smaller that the thickness of the nozzleblock, the pressure change can be substantial at the center of thearray. OVJP nozzles typically produce the narrowest line widths whenoperated in a limited pressure and flow range. Increasing the pressureinto which a nozzle is flowing may alter line width and decreasedeposition rate. That is, for the nozzle design of the embodiments ofthe disclosed subject matter, the pressure range may be from 100 to 200Torr, but the nozzles could be configured to work from 10 to 760 Torr.OVJP nozzles may be configured to operate in a wide range of depositionpressures, but neighbor effects may limit the size of the array, andspacing between nozzles for operating pressures.

FIGS. 10A-10B show computational fluid dynamics (CFD) modeled deposition(thickness) profile of a conventional linear array of four 30 micronwide simple nozzles spaced 500 microns apart. Delivery gas pressure forthis simulation is 15,000 Pa and the chamber pressure is 10,000 Pa. FIG.10A shows the stream lines emanating from the four nozzles. There is noflow between the second and third nozzles, which is caused by pumpingfrom the edges of the nozzle assembly. FIG. 10B shows the resultingdeposition profile. The two inner nozzles exhibit a lower depositionrate than the outer nozzles, and all deposition profiles are very broaddue to gas flow between nozzles directed toward the outer edges of thenozzle assembly.

To reduce and/or eliminate undesired deposition, broadening gas flowbetween nozzles must be reduced and/or eliminated. The embodiments ofthe disclosed subject matter provide a nozzle that reduces and/oreliminates nearest neighbor effects and enables densely packed OVJPnozzle arrays, as shown in FIG. 11. By including balanced gas supply andexhaust in each nozzle assembly, the net change in pressure and gas flowbetween nozzles is eliminated. Each nozzle includes three flow elements:a delivery channel for delivery gas and organic material, an exhaustchannel and a confinement gas channel (e.g., a three element nozzle).The combined flow of delivery gas and purge gas is balanced byevacuating an equivalent flow through the exhaust channel. The aperturesfor each of the delivery gas, confinement gas and exhaust flow channelsare arranged to confine the deposit resulting from the organic materialimpinging on the substrate and remove surplus organic material that doesnot adsorb to the substrate. FIG. 11 shows one configuration of flowchannels with an angled exhaust channel. Other configurations of flowchannels are possible.

FIG. 12 shows modeled stream lines of the delivery 511 and 512confinement gas flows entering from their respective sources,intersecting in the region between the print head and nozzle assembly513 and exiting through the exhaust channel 514. Spreading of thedelivery gas may be limited by the opposing flow of the confinement gas.

As shown in FIG. 11, each nozzle may be constructed with the deliverychannel in the center of the nozzle assembly. Exhaust channels may belocated adjacent to the sides of the delivery aperture. Two confinementchannels may be disposed adjacent to the exhaust channels, and fartherfrom the center nozzle.

The channel may form a layered structure with five flow channels (e.g.,a delivery channel, two exhaust channels and two confinement gaschannels) separated by non-flow regions. Viewed edge-on, the channelsform five apertures. The apertures may include apertures that arecommunicatively coupled to the confinement gas channels, the exhaustchannels, and the delivery channel. FIG. 13 shows a bifurcated deliverychannel, which appears as a pair of narrow apertures. In the substrateview of FIG. 13, each aperture is shown generally rectangular in shapewith the short axis perpendicular to the direction of travel over thesubstrate. As shown in FIG. 13, the delivery aperture has a shorterlength (long axis of the nozzle) than the exhaust and confinementapertures. The spacing and shape of the apertures and gas flow in eachchannel may be configured so as to produce a desired printed line width,having limited or no overspray. Process conditions may be set so the netflow from each nozzle assembly is zero, the flow into the nozzleassembly is equal to the flow out of the nozzle assembly, and there isno net pressure change between neighboring nozzles.

FIGS. 14A-14D show a schematic of a linear array of simple nozzles andcomputational fluid dynamics (CFD) analysis of nearest neighbor effectson the deposition patterns. FIG. 14A shows the aperture configuration ofthe three element nozzle assembly (e.g., a delivery channel, an exhaustchannel, and a confinement gas channel), and FIG. 14B is a cross-sectionview showing the flow channels on the nozzle assembly. FIG. 14C (i.e.,the “balanced flow”) shows the nozzle configuration used to model thethree element nozzle array of four nozzles (i.e., each nozzle of thefour nozzle array has three elements), where the modeled thicknessdistribution obtained using the nozzle array is shown in FIG. 14D.Process conditions for FIGS. 14A-14D are listed in Table 1.

TABLE 1 Process conditions used to obtain modeled results for FIGS.14A-14D. Conditions Delivery Width 30 μm Delivery Pressure 15,000 PaDelivery-Exhaust Separation 25 μm Exhaust Width 25 μm Exhaust Pressure5,000 Pa Exhaust-Confinement Separation 100 μm Confinement Width 25 μmConfinement Pressure 15,000 Pa Left Hand Pressure 5,000 Pa Right HandPressure 5,000 Pa

FIG. 10B and FIG. 14D show a comparison of the modeled results from afour nozzle array of simple nozzles (FIG. 10B) and a four nozzle arrayof three element nozzles (FIG. 14D). Comparison of the single nozzlestream lines shows that flow caused by the neighboring nozzle shifts thedeposition pattern in the direction of gas flow toward the perimeter ofthe nozzle array. The shift has two effects: (1) moving the center ofthe deposit, and (2) broadening the deposition. The three elementdeposition profile shows a well-defined peak shape with a width of 150μm (FIG. 14D). The simple nozzle profile (FIG. 10B) shows irregularlyshaped peaks with broad deposition. The deposition from the two innernozzles merges with the distribution from the outer nozzles. Pixels in adisplay may be spaced at regular intervals and organic material for thatpixel must be deposited so that no material from the pixel impinges onneighboring pixels. When the flux from a nozzle is shifted due to aneighboring nozzle, the tail of the Gaussian deposition distribution maymove into a neighboring pixel. If material does deposit on neighboringpixels the color, efficiency and lifetime may be adversely affected.Within each pixel, the deposited organic material must have uniformthickness and composition profiles. If the flux from a nozzle isaltered, the thickness profile will become less uniform, and the qualityof light emitted from each pixel will not be equivalent.

In addition to linear arrays on nozzles, two-dimensional arrays may bemade as shown in FIG. 15 and FIG. 16. FIG. 15 shows a two-dimensionalarray with deposition apertures aligned so that deposition fromapertures in successive rows would add the deposition from the firstrow. FIG. 16 shows a two-dimensional array having both aligneddeposition nozzles and staggered deposition nozzles. This configurationmay print lines with half the spacing of the array in FIG. 15 because ofthe staggered nozzles and would double print each line by having twoaligned nozzles, as in FIG. 15.

In view of the above, embodiments of the disclosed subject matter mayinclude a device having a nozzle, a source of material to be depositedon a substrate in fluid communication with the nozzle, a delivery gassource in fluid communication with the source of material to bedeposited with the nozzle, an exhaust channel disposed adjacent to thenozzle, and a confinement gas source in fluid communication with thenozzle and the exhaust channel, and disposed adjacent to the exhaustchannel.

A deposition device or system as disclosed herein may include aconnector configured to connect to an external vacuum source. Theconnector places an exhaust aperture, coupled to the exhaust channel, influid communication with the external vacuum source when connected tothe external vacuum source.

The exhaust channel of the device can be angled away from a delivery gasaperture, where the delivery gas aperture is in fluid communication withthe delivery gas source.

A confinement gas from the confinement gas source can be provided at atemperature lower than a delivery gas temperature. The confinement gasmay be provided by the confinement gas source at the same temperature asa delivery gas through additional apertures of the nozzle.Alternatively, the confinement gas from the confinement gas source maybe provided at a temperature greater than a delivery gas temperature.

The nozzle of the device may include a plurality of apertures. Thenozzle can include a delivery channel separator disposed within adelivery channel opening, where the delivery channel separator dividesthe delivery opening into two or more distinct apertures, and whereinthe delivery channel opening is in fluid communication with the deliverygas source.

The device can include a nozzle block having a delivery aperture and anexhaust aperture, where the delivery aperture is in fluid communicationwith the delivery gas source and the exhaust aperture is in fluidcommunication with the exhaust channel. One or more exhaust aperturesmay at least partially surrounds the delivery aperture within the nozzleblock. The delivery aperture may be defined by an edge of the nozzleblock and a channel in the nozzle block. The exhaust aperture may atleast partially surround the channel in the nozzle block.

The nozzle block may include one or more confinement gas apertures influid communication with the confinement gas source. The nozzle blockmay include a chiller plate disposed adjacent to the nozzle. The nozzleblock may include a plurality of nozzles. In some embodiments, theplurality of nozzles may be disposed in a linear arrangement within thenozzle block. Alternatively, the plurality of nozzles may be disposed ina staggered arrangement within the nozzle block.

A confinement gas from the confinement gas source may have at least thesame average molar mass as a delivery gas from the delivery gas source.Alternatively, the confinement gas from the confinement gas source has ahigher average molar mass than a delivery gas from the delivery gassource. The confinement gas source may be in fluid communication with anexternal confinement gas source that is external to the device.

The device may include a substrate holder disposed below the nozzle, forexample, as shown in FIG. 11. The substrate holder permits loading andunloading of the substrate and moves the substrate relative to thenozzle assembly during printing. The substrate holder may be disposed adistance from the nozzle sufficient to position a substrate 10-1000 μmfrom the nozzle. The substrate holder may be temperature controlled toremove heat transferred to the substrate during printing and maintainthe substrate at an optimum temperature for printing organic material.Temperature control may be accomplished with a cooling loop inside ofthe substrate holder that permits heat exchange fluid to flow in aclosed circuit between the substrate holder and a heat sink external tothe process chamber. Temperature control may also be achieved with athermoelectric device, and/or with helium backside cooling.

Embodiments of the disclosed subject matter may also provide a methodincluding ejecting a delivery gas and a material to be deposited on asubstrate from a nozzle, providing a confinement gas having a flowdirection opposing a flow direction of the delivery gas ejected from thenozzle; and providing a vacuum source adjacent to a delivery gasaperture of the nozzle.

The method may include providing the confinement gas at a temperaturelower than the ambient temperature below the nozzle.

The method may include providing the confinement gas at the sametemperature as a delivery gas through additional apertures of thenozzle. Alternatively, the method may provide the confinement gas at atemperature greater than a delivery gas temperature. The confinement gasmay be provided from an ambient chamber.

The confinement gas may be provided from one or more nozzles in fluidcommunication with a confinement gas source external to a processchamber in which the nozzle is disposed. The confinement gas may beprovided through a pair of apertures of the nozzle. The method mayinclude chilling the confinement gas.

The method may include rastering the nozzle over a substrate disposedadjacent to the nozzle to form a continuous film above the substrate.

The method may include providing a plurality of delivery gases and aplurality of materials to be deposited on the substrate via the nozzle,wherein the nozzle has one or more apertures.

Embodiments of the disclosed subject matter may provide a nozzleassembly having a plurality of nozzles, with each nozzle comprising atleast three separate types of flow channels which include a deliverychannel to provide a delivery gas including an organic material, exhaustchannels arranged adjacent to the delivery channel to evacuate gas froman area disposed between the nozzle assembly and a substrate, andconfinement gas channels arranged adjacent to the exhaust channels tosupply a confinement gas flow.

The nozzles of the nozzle array may be arranged to form a linear array.Alternatively, the nozzles of the nozzle assembly may be arranged toform a two dimensional array.

A sum of gas flows from the delivery channel and the confinement gaschannels may be equal to a gas flow from the exhaust channels. A gasflow from the exhaust channels is greater than a sum of gas flows fromthe delivery channel and the confinement gas channels of the nozzleassembly. Alternatively, a gas flow from the exhaust channels may beless than a sum of gas flows from the delivery channel and theconfinement gas channels of the nozzle assembly.

The nozzle assembly may include a nozzle block having a plurality ofnozzles arranged in a linear or two dimensional (2D) array, and gaschannels disposed on a bottom surface of the nozzle block.

As shown in FIG. 17, the nozzle block of the nozzle assembly may includeconfinement distribution channels that provide a low impedance path forthe flow of confinement gas from a process chamber ambient or a separategas supply to the confinement channels of each nozzle assembly. In thiscase, the confinement distribution channel may be the region between thenozzle assembly and the substrate adjacent to the deposition zoneunderneath the delivery and exhaust apertures. The confinementdistribution channel may place the chamber ambient in fluidcommunication with each nozzle assembly. Confinement distributionchannels may be integrated within the nozzle block or they may berecesses in a surface of the nozzle block adjacent to the substrate. Thewidened gas flow paths formed between the recesses in the die surfaceand the substrate form the confinement distribution channels. In anembodiment of the disclosed subject matter, the confinement distributionchannels may be formed from recesses in the substrate-adjacent edge ofthe nozzle block that have a constant cross-section in a plane parallelto a plane of the nozzle block. The confinement distribution channelsmay be arranged so that one is adjacent to each side of each nozzle.

The delivery gas may have lower molecular weight than the confinementgas. In some embodiments, the delivery gas and confinement gas may bethe same gas. The molecular weight of the delivery gas may be greaterthan the molecular weight of the confinement gas.

In some embodiments of the disclosed subject matter, a depositionpattern from each nozzle of the nozzle assembly may be equivalent to oneanother.

Embodiments of the disclosed subject matter may provide forming a nozzleassembly having a plurality of nozzles, with each nozzle comprising atleast three separate types of flow channels, including forming a firstchannel to provide a delivery gas including an organic material, forminga plurality of second channels arranged adjacent to the first channel toevacuate gas from an area disposed between the nozzle assembly and asubstrate, and forming a plurality of confinement gas channels arrangedadjacent to the plurality of second channels to supply a confinement gasflow.

Embodiments of the disclosed subject matter may also provide adeposition system having a nozzle assembly having a plurality ofnozzles, with each nozzle comprising at least three separate types offlow channels which include a first channel to provide a delivery gasincluding an organic material, a plurality of second channels arrangedadjacent to the first channel to evacuate gas from an area disposedbetween the nozzle assembly and a substrate, and a pair of confinementgas channels arranged adjacent to the plurality of second channels tosupply a confinement gas flow.

Embodiments of the disclosed subject matter may further provide adisplay fabricated using a nozzle assembly to deposit organic materials,the nozzle assembly having a plurality of nozzles, with each nozzlecomprising a plurality of separate types of flow channels which includea first channel to provide a delivery gas including an organic material,a plurality of second channels arranged adjacent to the first channel toevacuate gas from an area disposed between the nozzle assembly and asubstrate, and a plurality of confinement gas channels arranged adjacentto the plurality of second channels to supply a confinement gas flow.

EXPERIMENTAL

The gas curtain parameter space was studied using both two dimensionalDSMC and computational fluid dynamics (CFD) techniques. The structurewas treated in cross-section as shown in FIG. 4, with its in-planeextents being treated as infinite. The importance of edge effects wasestimated by simulating the same structure using three dimensional CFD.This was used to generate a map of organic flux onto the plane of thesubstrate shown in FIG. 18. Regions of high organic flux 801 correlatewith the expected size and shape of the printed spot size underneath thenozzle assembly. The intensity of organic flux is given by grayscale802. The simulation predicted well-controlled edge effects that are notexpected to degrade overall printing performance.

A set of dies containing gas curtain depositors was fabricated from apair of Si wafers using deep reactive ion etching (DRIE) to formstraight sidewalled trenches. Mirror image structures on the etchedfaces of the wafers were aligned to each other and the wafers pair wasbonded using Au—Ge solder. This process formed channels within the die.Vertical sidewalls of the trenches became the sides of the channels. Therelief between the polished surface of one Si wafer and the bottom of anetched trench on the other wafer defined the depth of some channels.

Deeper channels were formed by matching etched trenches so that thechannel depth was the sum of the etch depth. Vias to address theupstream ends of the channels were etched through the outside surface ofthe bonded wafer pair with DRIE. The organic vapor and delivery gaschannels were addressed through vias on one side of the wafer, while theexhaust channels were addressed through vias on the other side. Dieswere singulated from the wafer pair using either DRIE or stealth dicingto make very (<10 μm) precisely positioned cuts with minimal kerf. Theapertures of both the nozzles (e.g., delivery channels) and exhaustchannels were defined by the intersection of internal channels withinthe die and its lower edge formed by the dicing process. The structureincludes a set of five nozzles, each of which contains a central organicsupply channel flanked by exhaust channels to remove recoiled organicmaterial.

FIG. 19 shows a scanning electron micrograph of the features etched intoone side of the wafer pair, which illustrates the internal structure ofan example die according to an embodiment of the disclosed subjectmatter. The delivery channel 901 runs from a widened feed channel 902 toa breakout line 903 at the base of the die defining its underside.Exhaust apertures 904 on either side of the nozzle may allow surplusorganic vapor and delivery gas to escape through exhaust channels 905 tolow pressure regions outside of the chamber. Recesses etched into theunderside of the die 906 may serve as confinement distribution channelsthat facilitate the flow of confinement gas from the chamber ambient tothe underside of the nozzle assembly and thus improve the uniformity ofthe resulting gas curtain. The structure shown in FIG. 19 was alignedand bonded to a second Si wafer containing mirror images of structures904 and 905. This resulted in a sealed structure in which the nozzle waseffectively surrounded by exhaust apertures.

The features of a nozzle assembly are visible from the outside when thedie is viewed edge on. The bottom edge of the die, which faces thesubstrate during operation, is shown in FIG. 20A. Organic vapor isejected onto the substrate through a delivery aperture 1001. The nozzleassembly moves relative to the substrate in a direction parallel to thelong axis of the delivery aperture. The delivery aperture is surroundedon both of its long sides by apertures of exhaust channels 1002. Theexhaust apertures of the exhaust channels collect excess organic vaporto prevent it from condensing onto the substrate outside of the intendeddeposition zone. The long axes of the exhaust apertures of the exhaustchannels extend beyond those of the delivery aperture to preventspreading of organic vapor due to edge effects near the ends of thecentral nozzle.

Confinement gas enters along the edges of the bottom face of the nozzleassembly. The flow of the confinement gas from the chamber ambient isfacilitated through confinement distribution channels cut into theunderside of the nozzle assembly 1003. These channels are on both sidesof the nozzle assembly and run parallel to the long axis of the nozzleaperture (e.g., the aperture of the delivery channel). They may create auniform flow of confinement gas from their inner edges to the exhaustchannel, creating a gas curtain to prevent the migration of organicvapor outside of the intended deposition zone. Confinement gas can alsoenter along the die edges parallel to the short axis of the nozzleaperture 1004. The channels within the die that connect to the deliveryand exhaust apertures are fabricated by mating etched surfaces of two Siwafers with features such as those shown in FIG. 19. The wafers, and thesingulated dies resulting from them are bonded together with Au—Geeutectic solder, such as described in U.S. Patent Publication2014/0116331, the disclosure of which is incorporated by reference inits entirety. The solder joint 1005 runs horizontally through themidsection of the die.

A simulation was performed to identify a set of favorable processconditions in advance of upcoming experiments. A pressure of 100 Torr ata confinement gas inlet, such as inlet 403 in FIG. 4, is expected to benear optimal. The increase in diffusion coefficient and organic moleculemean free path below 10 Torr limits the effectiveness of the gascurtain. Conversely, operating at pressures significantly higher than300 Torr tends to restrict diffusive transport of organic vapor to thesubstrate. The nozzle assembly is heated to prevent condensation oforganic vapor. It operates at approximately 300° C., as does theevaporation and mixing hardware upstream of it. The base of the nozzleassembly is held 50 μm over the substrate.

Confinement gas can be either fed into the deposition zone throughdedicated nozzles or drawn from the chamber ambient, as in the in theinitial experiments. Since the organic vapor jet delivery gas andconfinement gas need not come from the same source, dissimilar gases maybe used. A light delivery gas such as helium can be used to increase therate of diffusion of organic vapor underneath the nozzle. A heavier gassuch as argon or sulfur hexafluoride can suppress both organic vapordiffusion and heat transfer to the substrate in the confinement gas.Using a light delivery gas and heavy confinement gas, broadens the rangeof suitable ambient operating pressures, possibly up to atmosphericpressure. The capability to perform OVJP at atmospheric pressure hasbeen previous demonstrated, but at substantially coarser resolution.

Interaction between molecules of organic vapor and the delivery gas wasmodeled using the Direct Simulation Monte Carlo method of Bird. Thedelivery gas flow field was computed first. Tracers representing organicvapor were then introduced into this flow field. Their trajectories aredetermined by interactions with delivery gas molecules. A heliumdelivery gas was modeled as hard spheres having a diameter of 2.8×10⁻¹⁰m and a mass of 0.004 kg/mol. Organic molecules were modeled as having adiameter of 1×10⁻⁹ m and a mass of 0.5 kg/mol, typical of OLEDmaterials.

This method is most widely used for flows in which Kn is greater than0.1, in which molecules have large mean free paths relative to theircontainers. While this was not true of most operating conditions understudy, an atomistic treatment was required to determine the effect ofsticking coefficient on the paths followed by organic vapor molecules.Non-unity sticking can be modeled by treating the sticking coefficient αas an accommodation coefficient commonly used to model the thermalinteraction between gas molecules and a boundary. An organic moleculecrossing the substrate boundary has a probability of thermalizing withits boundary. Since the substrate is below the molecule's sublimationtemperature, a thermalized molecule becomes adsorbed. Conversely, anincident organic molecule has 1−α probability of not thermalizing withthe boundary. If so, it remains in the vapor phase and spectacularlyreflects from the substrate boundary.

Once it was established that the thickness distribution of featuresgenerated by the nozzle assembly are relatively insensitive to stickingcoefficient, computational fluid dynamics software (COMSOL, Burlington,Mass.) was used to model gas flow and the propagation of organic vaporthrough it. The transport properties of organic vapor in nitrogen gaswere calculated from kinetic theory. Two dimensional simulationsrendering the nozzle assembly in cross-section were used to study theparameter space of its operation, as shown in FIGS. 5-7. A morecomputationally intensive three dimensional model was used to confirmthe simpler model's results for the most promising cases. FIG. 18 showsthe results of one such example simulation.

An embodiment of a deposition system as described herein with respect toFIG. 20A was tested by fabricating a structure as shown in FIG. 20B, bygrowing an emissive layer 1012 of a phosphorescent OLED. The emissivelayer included a green emitting organic electrophosphorescent compoundmixed with an organic host deposited with organic vapor jet printing ofan embodiment of the disclosed subject matter. The OLED was fabricatedon a glass substrate 1011 and included an anode layer, a hole injectionlayer, and a hole transport layer 1013 deposited underneath the emissivelayer by standard methods. An electron transport layer and electroninjection layer 1014 were deposited over the emissive layer, as was acathode 1015. A region containing as little as 0.2 Å ofelectrophosphorescent material between layers 1013 and 1014 willluminesce brightly when current is applied, making this structurerelatively effective for determining the fate of deposited material.

FIGS. 21A-21B show examples of lines printed by two different organicvapor jet nozzle assemblies. The line in FIG. 21A was printed by an aircurtain nozzle assembly according to an embodiment, similar to thestructure shown in FIGS. 20A-20B. The chamber ambient was 100 Torr N₂.Helium delivery gas laden with organic vapor was fed through each 20 by150 μm nozzle in the die at 4 sccm, while approximately 10 sccm of gaswas withdrawn through each pair of 40 by 450 μm exhaust channelsflanking the nozzle (e.g., the delivery channel). The resulting printedfeature had a center portion 1101 approximately 195 μm wide thatphosphoresced brightly. It was surrounded by a dark field 1102 thatshowed no sign of contamination by printed material. The transitionbetween these two zones 1103 was 25 μm wide. In contrast, FIG. 21B showsconventional results achieved without a gas curtain. The center of theprinted line portion 1104 is 162 μm wide, but it is surrounded on eachside by a 130 μm wide luminescent border 1105, indicating the presenceof extraneous material. Removal of this extraneous material by the gascurtain results in features that are 46% narrower.

It is understood that the various embodiments described herein are byway of example only, and are not intended to limit the scope of theinvention. For example, many of the materials and structures describedherein may be substituted with other materials and structures withoutdeviating from the spirit of the invention. The present invention asclaimed may therefore include variations from the particular examplesand preferred embodiments described herein, as will be apparent to oneof skill in the art. It is understood that various theories as to whythe invention works are not intended to be limiting.

1. A device comprising: a nozzle; a source of material to be depositedon a substrate in fluid communication with the nozzle; a delivery gassource in fluid communication with the source of material to bedeposited with the nozzle; an exhaust channel disposed adjacent to thenozzle; and a confinement gas source in fluid communication with thenozzle and the exhaust channel, and disposed adjacent to the exhaustchannel.
 2. The device of claim 1, further comprising a connectorconfigured to connect to an external vacuum source.
 3. The device ofclaim 2, wherein the connector places an exhaust aperture, coupled tothe exhaust channel, in fluid communication with the external vacuumsource when connected to the external vacuum source.
 4. The device ofclaim 1, wherein the exhaust channel is angled away from a deliveryaperture, wherein the delivery aperture is in fluid communication withthe delivery gas source. 5-7. (canceled)
 8. The device of claim 1,wherein the nozzle comprises a plurality of apertures.
 9. The device ofclaim 8, wherein the nozzle comprises a delivery channel separatordisposed within a delivery channel opening, wherein the delivery channelseparator divides the delivery opening into two or more distinctapertures, and wherein the delivery channel opening is in fluidcommunication with the delivery gas source.
 10. The device of claim 1,further comprising a nozzle block, wherein the nozzle block comprises adelivery aperture and an exhaust aperture, wherein the delivery apertureis in fluid communication with the delivery gas source and the exhaustaperture is in fluid communication with the exhaust channel.
 11. Thedevice of claim 10, wherein the exhaust aperture at least partiallysurrounds the delivery aperture within the nozzle block.
 12. The deviceof claim 10, wherein the delivery aperture is defined by an edge of thenozzle block and a channel in the nozzle block.
 13. The device of claim12, wherein the exhaust aperture at least partially surrounds thechannel in the nozzle block.
 14. The device of claim 10, wherein thenozzle block comprises a confinement gas aperture in fluid communicationwith the confinement gas source.
 15. The device of claim 10, wherein thenozzle block further comprises a chiller plate disposed adjacent to thenozzle.
 16. The device of claim 10, wherein the nozzle block comprises aplurality of nozzles.
 17. The device of claim 16, wherein the pluralityof nozzles are disposed in a linear arrangement within the nozzle block.18. The device of claim 16, wherein the plurality of nozzles aredisposed in a staggered arrangement within the nozzle block. 19-20.(canceled)
 21. The device of claim 1, wherein the confinement gas sourceis in fluid communication with an external confinement gas source thatis external to the device.
 22. The device of claim 1, further comprisinga substrate holder disposed below the nozzle.
 23. (canceled)
 24. Thedevice of claim 22, further comprising a temperature controller tocontrol the operating temperature of the substrate holder. 25-34.(canceled)
 35. A nozzle assembly comprising: a plurality of nozzles,with each nozzle comprising at least three separate types of flowchannels which include: a delivery channel to provide a delivery gasincluding an organic material; exhaust channels arranged adjacent to thedelivery channel to evacuate gas from an area disposed between thenozzle assembly and a substrate; and confinement gas channels arrangedadjacent to the exhaust channels to supply a confinement gas flow.36-49. (canceled)
 50. A deposition system, comprising: a nozzle assemblyhaving a plurality of nozzles, with each nozzle comprising at leastthree separate types of flow channels which include: a first channel toprovide a delivery gas including an organic material; a plurality ofsecond channels arranged adjacent to the first channel to evacuate gasfrom an area disposed between the nozzle assembly and a substrate; and apair of confinement gas channels arranged adjacent to the plurality ofsecond channels to supply a confinement gas flow.
 51. (canceled)